A. Field of the Invention
The present invention relates generally to the communications field, and, more particularly to a fiber optic cable winding tool for winding predetermined lengths of fiber optic cables and predetermined diameter coils of fiber optic cables used in the communications field.
B. Description of the Related Art
Most communication equipment is designed to be interconnected with communication cables having predetermined lengths. However, it is a problem in the field of communication cable installation to provide accurate predetermined lengths of communication cables without damaging the communication cables by the provision of tight bends, or inappropriate use of fasteners, or inadequate support to the communication cables. Such communication cables include conventional telephone cable having a plurality of copper conductors, coaxial cable, optical fiber, or the like. In all of these applications, the minimum radius of curvature of the communication cable is well defined, and bending the communication cable in a tighter bend can cause damage to the communication medium housed within the cable.
This problem is further heightened when fiber optic cables are used. Glass fibers used in such cables are easily damaged when bent too sharply and require a minimum bend radius to operate within required performance specifications. The minimum bend radius of a fiber optic cable depends upon a variety of factors, including the signal handled by the fiber optic cable, the style of the fiber optic cable, and equipment to which to fiber optic cable is connected. For example, some fiber optic cables used for internal routing have a minimum bend radius of 0.75 inches, and some fiber optic cables used for external routing have a minimum bend radius of 1.0 inches.
Damaged fiber optic cables may lead to a reduction in the signal transmission quality of the cables. Accordingly, fiber optic cables are evaluated to determine their minimum bend radius. As long as a fiber optic cable is bent at a radius that is equal to or greater than the minimum bend radius, there should be no reduction in the transmission quality of the cable. If a fiber optic cable is bent at a radius below the minimum bend radius determined for such cable, there is a potential for a reduction in signal transmission quality through the bend. The greater a fiber optic cable is bent below its minimum bend radius, the greater the potential for breaking the fibers contained in the cable, and the shorter the life span of the cable.
For example, in a telephone switching office, the various switching components are split onto different printed circuit boards (PCBs). Fiber optic cables may be used to route the signals between the different PCBs or between components on a single PCB. In a conventional arrangement, the PCB is generally placed in a shelf or rack alongside other such PCBs.
The fiber optic cables are used for transferring signals between reception ports and electro-optical converters provided on the PCB or PCBs. Fiber optic cables generally come in three-foot and six-foot lengths with connectors provided at the ends thereof. However, the PCB may have a width of only several inches. Thus, the extra lengths of the fiber optic cables need to be stored on or near the PCB, using space in the optical communications equipment that is becoming more and more valuable as equipment becomes more densely packed. If the extra lengths of fiber optic cables are not stored, then they are susceptible to damage since they will freely hang in the equipment and may be pulled, snagged, or bent beyond their minimum bend radii.
Typically, pre-spooled fiber optic cable having a predetermined diameter is stored in cassettes containing optical communications equipment. For example, as shown in U.S. Pat. No. 5,778,132, assigned to the assignee of the present application, CIENA Corporation, depicts an amplifier module in FIG. 3 with parts separated to illustrate cassette construction and inter-engagement with adjacent cassettes. Each cassette includes a flat, tray-like base 111A, B, C, for receiving optical components and optical fiber. Cassette walls 112A, B, C define an interior curved surface which corresponds to a permissible bend radius for the optical fiber employed in the amplifier. A pair of retaining walls 123A, B, and C in each cassette define an outer track for fiber retention against the interior cassette walls and additionally serve to separate the fiber from other optical components within the cassette. Fiber retaining clips 115A, B, C extend from the cassette walls to assist in fiber guidance and organization within the cassette. Fiber guiding projections 116A, B, and C extend from the base of the cassette for directing the fiber toward the fiber retaining clips to further aid in fiber organization within the cassette, particularly for fibers which extend to or from optical components placed within the cassette. The configuration of the optical cassettes permits fiber to be wound within the cassette or, alternatively, pre-spooled fiber may be placed within the cassette and under the fiber retaining clips.
Devices that utilize pre-spooled fiber optic cable include erbium-doped fiber amplifiers (EDFA) and discrete Raman amplifiers. Such amplifiers utilize a length of fiber in which to amplify the optical signal. In the EDFA, this length of fiber is doped with Erbium. The discrete Raman amplifier typically utilizes a fiber type that is tuned or otherwise suitable for stimulated Raman scattering amplification. These and other devices often require a length of optical fiber that should be spooled in some fashion for the reasons discussed above.
The spool of fiber optic cable used by such devices preferably has a certain spool diameter because the spool may be housed in a package such as a cassette that has close tolerances. The close tolerances in such packages make installation and removal of pre-spooled fiber optic cables very difficult. Sometimes the spool diameter of the fiber optic cable needs to be increased or decreased depending upon its fit within the package (e.g. cassette). Furthermore, the device utilizing the fiber spool often needs a specific length of optical fiber (e.g. the EDFA typically uses a predetermined length of Erbium doped fiber to perform the amplification). Thus, the length of the fiber optic cable being spooled is typically set while the spool diameter may need to be varied depending upon the packaging of the fiber spool.
It is thus desirous to create spools of fiber optic cable having different diameters. Unfortunately, conventional fiber optic cable spoolers require a different, dedicated reel for each diameter desired. The operator or user of a conventional spooler spends valuable time setting up for different diameters of fiber optic cable. Furthermore, it is very difficult to remove spooled fiber optic cables from conventional spoolers, without damaging or destroying the fiber optic cable.
Thus, there is a need in the art to provide a means for providing multiple, accurate, predetermined lengths and spool diameters of fiber optic cable windings used in optical communications systems that may be quickly and easily utilized by an operator and prevent the fiber optic cables from being damaged or bent beyond their minimum bend radii.
The present invention solves the problems of the related art by providing a fiber optic cable winding tool for providing accurate predetermined lengths of fiber optic cables, and having a substantially circular winding drum or spool made up of peripheral elements that are radially adjustable to different diameters.
As embodied and broadly described herein, the present invention is broadly drawn to a fiber optic cable winding tool having concentric upper and lower disk-shaped bases that are rotatable relative to each other. Four quarter-circle spools are slidably mounted on the upper base, and are radially adjustable towards and from the central axis of the upper base via radial slots formed in the lower base. Each spool has a fiber optic cable contacting surface with a radius of curvature exceeding a minimum bend radius of the fiber optic cable. The radial slots communicate with corresponding arcuate slots formed in the lower base, and roller guides are provided through each radial slot and its corresponding arcuate slot and connects to a corresponding spool. When the upper and lower bases are rotated relative to each other, the spools move either towards or away from the central axis of the upper base, enabling a spool diameter to be set. A thumb screw is also provided to bear against the rear base and maintain the desired diameter setting. The tool further includes a travel stop guide formed on the periphery of the upper disk-shaped base to prevent the upper and lower disk-shaped bases from rotating relative to each other, enabling predetermined diameters to be set. The radial and arcuate slots permit the spools to be radially collapsed towards the central axis of the upper disk-shaped base after winding the fiber optic cable to permit removal of the fiber optic cable from the spools.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.